...

This wasn't the fact. Again monetdb consumed all my memory and when loading finished it indicated that it was still doing something (CPU @ ~20%). log records have to be written, your OS may kick in to flush dirty pages, reloading swapped out processes, ....

The following might not apply to Linux, but still: under windows, suddenly flushing dirty pages from large memory mapped files can severly degrade the system performance ("stalled"). I know windows has settings to limit the amount of dirty pages that may accumulate without flushing. Maybe Linux has something similar and maybe this helps here. Please keep me in the loop if you try this route. Jens